Equilibrium Flashcards
Equilibrium
Occurs when forward and reverse reactions are proceeding at equal rates
Takes place in a closed system
Composition of an equilibrium mixture remains constant and reactions occur at the same rate
Reverse Reaction is Favored
Rate of the reverse reaction is greater than the forward reaction
Reaction Quotient
For a reversible reaction, the relative amounts of reactants and products at any given time can be written as a ratio of products over reactants
aA + bB -> cC + dD
Qc= [C]^c * [D]^d/ [A]^a * [B]^b
Qp= PC^c * PD^d/ PA^a * PB^b
Always leave solids and liquids out of the equation
Forward Reaction is Favored
Forward reactions is greater than the rate of the reverse
Concentrations or partial pressures change
Equilibrium Constant
When the system is at equilibrium, the equilibrium constant is used instead of Q (same formula as Q)
When does the k constant change
If there is a temperature change
Magnitude of K Values
K>1 products are Favored at equilibrium
K<1 reactants are favored
K=1 there are equal numbers of reactants and products
k>10^3 reaction goes to completion
K<10^-3 reaction does not move in the forward direction
Manipulating balanced equation, what happends to k
Reversing reacttion, turn k into recirpocal
Reaction is multiplied, k is raised to the power
Two or more reactions are added to get her, k is the product
ICE Tables
Shows Initial, change, and equilibrium concentrations or pressures for the reaction
Calculating Q to determine the reaction will proceed rules
Q=K system of equilibrium
Q>K too many products, proceeds to left
Q<K too many reactants, proceeds to the right
Adding/subtracting substances
Addition of a substance will shift the system to use up the substance
Does not apply to solids and liquids
Changing volume or total pressure
Reduce volume or increase total pressure causes system to shift to the side with less moles of gas
If total pressure is changed from an insert gas, it has not effect bc the partial pressure of each substance stays the same
Addition of a Catalyst
Catalyst lowers the activation energy in both directions but does not shift the Keq
Change in Temperature
Endothermic process=heat is like a reactant=increase temp=drives reaction to right and increases k
Exothermic process=heat is like a product=increase temp=drives reaction to left and decreases k
Solubility
Amount of a salt that will dissolve to form a saturated solution at a specific temperature Molarity (g/L)
Saturated Solution
There must be some dissolved solute in order to consider solution saturated
Ksp
Solubility product equilibrium constant
Shows the concentration of dissolved ions at equilibrium
The value only changes with temperature changes
Comparing Salt Solubility
Use the x value from an ICE table
Will a Precipitate Form?
Q>Ksp precipitation occurs until Q=Ksp
Q=Ksp then the system is at equilibrium
Q<Ksp then the reaction will proceed to the right and the solid will dissolve
Common-Ion Effect
The solubility of a slightly soluble salt decreases in the presence of a second solute containing a common ion
AKA having initial concentration leads to less decreasing
When is X negligible in ICE
When there’s a quadratic if there is a starting initial amount and Ksp<10^-3
pH and Solubility
Salts that have a hydroxide ion or a weak base have an impacted solubility by addition of acids/bases
If weak base=solubility is impacted by pH
How to know if it’s a weak base
Place H+ in front of the anion and it forms a weak base then it’s a weak acid
Enthalpy of Dissolution
Enthalpy is a measure of the heat content of a system
- = favorable or more likely to occur
+ = unfavorable or less likely
